class Box{
    constructor(){
        this.num=3;
    }
    play(){
//                this--->obj5 也就是通过new实例化的对象
//                console.log(this.num);
        console.log(this===obj5);
        console.log(this.num)
    }
}
let obj5=new Box();
obj5.play();
let obj6=new Box();
obj6.play();